大天顶角的到达角起伏

基于修正Kolmogorov谱,运用相位结构函数的平方近似,导出了适用于大天顶角传输的到达角起伏方差及其功率谱的解析表达式.研究结果表明,新导出的方差表达式在任意天顶角都是适用的.散射盘尺度和接收孔径对到达角起伏起平滑作用,当接收孔径远大于散射盘尺度时,由于孔径平滑作用,导出的表达式在任意天顶角都可以近似为弱起伏理论给出的结果；当接收孔径小于散射盘尺度时,散射盘尺度的平滑作用明显,接收孔径的平滑作用相对较小,传统的到达角起伏理论仅在小天顶角是适用的,在大天顶角必须用新导出的方差表达式.当接收孔径D<25 cm时,弱起伏理论给出的表达式的适用范围被限制在小于50°~70°的天顶角内.

Angle-of-arrival Fluctuation at Large Zenith Angles

Based on the modified Kolmogorov spectrum and quadratic structure function approximation,the expressions are derived for the variance and power spectrum of the angle-of-arrival fluctuation at large zenith angles.The validity of the derived expression extending into the any zeniths is evidenced by the simulations.When the receiving aperture is much larger than the scattering disk scale,the aperture-smooth effect is remarkable and the derived variance approximates the result given by weak-fluctuation theory for any zenith;when the receiving aperture is much smaller than the scattering disk scale,the low-pass filter effect of the scattering disk scale is dominating and weak-fluctuation theory is valid only for small zeniths.In the cases that D<25 cm,the derived result is in good agreement with conventional weak-fluctuation theory for zenith angles less than 50 to 70 deg,but departure from weak-fluctuation theory is predicted by the new models for larger zenith angles.